Topic: Article,

Best Answer Explained in Below-:

In the phrase "He went to the school on--foot," the correct answer is D) no article. This is because the expression "on foot" is a fixed idiomatic phrase in English that describes traveling by walking rather than using any form of transportation. When used this way, it does not require an article.

In English, certain phrases function as complete units of meaning and do not necessitate articles for clarity or grammatical correctness. "On foot," for example, is one such idiom that conveys the idea of walking efficiently, and adding an article would be grammatically incorrect.

Additionally, we often see similar phrases such as "by car," "by bus," or "on horseback," where the absence of an article is standard. Each of these phrases operates under the same logic: they inherently define a mode of transportation without needing further specification. Thus, the absence of an article before "foot" is what makes D) no article the correct answer in the given context.